Metal casting

ABSTRACT

Apparatus, methods and molds for casting metal in an evacuatedinert gas atmosphere. The apparatus comprises a sealable melting and mold pouring chamber having a sealable loading compartment mounted thereon with a conduit having a valve communicating therebetween and a sealable mold container having a bottom opening for sealing around the lower open end of a gas permeable refractory shell mold sealingly supported therewithin and extending downwardly therebeyond. Power means supports the container from above for movement between the chamber and compartment through the conduit to a melting crucible within the chamber directly beneath the container. The mold is loaded and unloaded with the container in raised position within the compartment while maintaining the chamber in evacuated condition by closure of the valve. A movable drip guard is mounted within the loading compartment between the valve and the container in its raised position. The refractory, gas permeable, shell mold preferred has a lower open end with a central vertical riser passage and may have a plurality of overlapping mold cavities clustered thereabout connected to the riser passage by gate passages. The cross section area dimension of the riser passage is at least one inch and five times as great as the cross section area dimension of a gate passage, so that molten metal can be drained from the riser passage to provide discrete unconnected cast parts from a single mold after the mold is separated from them.

United States Patent 1191 Chandley et a1.

1 1 Feb. 4, 1975 METAL CASTING [75] Inventors: George D. Chandley; JohnN. Lamb,

both of Amherst, NH.

{73] Assignee: Hitchiner Manuiacturing C0,, lnc.,

Milford, NH.

[22} Filed: Dec. 4, 1972 [21] App]. No.: 312,138

[52] US. Cl 164/255, 164/256, 164/306, 164/363, 164/62, 164/66, 164/63,249/120 [51] Int. Cl 822d 27/16 [58] Field of Search 164/306, 309, 61,62, 257, 164/262, 77, 63, 65,119, 63, 361,129, 363.

Primary Examiner- Francis S. Husar Assistant Examiner-V. K. Rising [57]ABSTRACT Apparatus, methods and molds for casting metal in anevacuated-inert gas atmosphere. The apparatus comprises a sealablemelting and mold pouring chamber having a scalable loading compartmentmounted thereon with a conduit having a valve communicating therebetweenand a scalable mold container having a bottom opening for sealing aroundthe lower open end of a gas permeable refractory shell mold sealinglysupported therewithin and extending downwardly therebeyond. Power meanssupports the container from above for movement between the chamber andcompartment through the conduit to a melting crucible within the chamberdirectly beneath the container. The mold is loaded and unloaded with thecontainer in raised position within the compartment while maintainingthe chamber in evacuated condition by closure of the valve. A movabledrip guard is mounted within the loading compartment between the valveand the container in its raised position. The refractory, gas permeable,shell mold preferred has a lower open end with a central vertical riserpassage and may have a plurality of overlapping mold cavities clusteredthereabout connected to the riser passage by gate passages. The crosssection area dimension of the riser passage is at least one inch andfive times as great as the cross section area dimension of a gatepassage, so that molten metal can be drained from the riser passage toprovide discrete unconnected cast parts from a single mold after themold is separated from them.

6 Claims, 9 Drawing Figures WAG Q WIIIIIIJ SHEEI 2 OF 5 'III III [FIG.

PATENTED sum 30F 5 1 METAL CASTING This invention relates to metalcasting apparatus, methods and molds and more particularly to thecasting of metal in an evacuatedinsert gas atmosphere and the casting ofa plurality of discrete unconnected parts in a single mold.

The precision casting on a high production basis of metals which must becast in an evacuated or inert gas atmosphc re has long been a problem.In part, this is due to the time necessary to establish the requiredseals and to evacuate the apparatus. especially insofar as therelatively large melting and pouring chamber is concerned. There arealso problems caused by the inclusion in the cast parts of dross orother impurities present on the surface of the molten metal.Additionally there are problems in separating the cast parts from thesolid metal riser connecting them, which make necessary relatively wideseparation between the mold cavities.

Accordingly, it is a major object of the invention to provide muchimproved apparatus, methods and molds for casting metal in anevacuated-inert gas atmosphere and one capable of operating in muchreduced cycle times.

It is another object of the invention to provide a dross and impurityfree molten metal surface for introduction into the mold.

It is still another object of the invention to provide novel methods andmolds which provide automatic separation of the cast parts from oneanother and so make possible greatly increased part packing within themold.

This is accomplished, according to one aspect of the invention, byproviding, preferably in combination with a scalable melting and moldpouring chamber having a scalable loading compartment mounted thereonand valve and conduit means communicating therebetween, that improvementwhich consists of a scalable mold container having a bottom opening forsealing around the lower open end of a gas permeable mold supportedtherewithin and extending downwardly therebeyond and power meanssupporting the container from above for movement between the chamber andcompartment through the valve and conduit means. Preferably, the moldcontainer has independent upper and lower relatively movable cupelements supported by suitable fluid actuated pistons for verticalmovement. A melting crucible for holding molten metal is mounted withinthe chamber directly beneath the container. Means are provided forselectively varying the pressure of the chamber, compartment andcontainer to fill the mold after lowering the container with the loweropen end of the mold beneath the surface of molten metal in thecrucible. The mold is loaded and unloaded with the container in raisedposition within the loading compartment while maintaining the chamber inevacuated condition by closure of the valve means. A movable drip guardmay be mounted within the loading compartment between the valve andconduit means and the mold container in its raised position.

In another aspect, the invention provides dross and impurity free moltenmetal by inductive stirring in the crucible to cause outward surfacemovement to carry impurities away from the central area of the crucibleto which the mold opening is introduced.

The invention, in still another aspect, provides a novel mold and methodof casting in a refractory, gas permeable, shell mold comprisingproviding a mold having a lower open end with a central vertical riserpassage having a plurality of preferably overlapping mold cavitiesclustered thereabout and connected to the riser passage by gatepassages. The cross section area dimension of the riser passage is atleast about 1 inch and five times as great as the cross section areadimension of a gate passage, so that molten metal can be drained fromthe riser passage after solidification in the mold cavities to providediscrete unconnected cast parts from a single mold after the mold isseparated from them.

For the purpose of more fully explaining the above and further objectsand features of the invention, reference is now made to the followingdetailed description of preferred embodiments thereof, taken togetherwith the accompanying drawings, wherein:

FIG. I is a side view, partly broken away and in section, illustratingapparatus according to the invention;

FIGS. 2 and 3 are, respectively, detail side and top sectional views ofa gas permeable shell mold of the invention mounted in the apparatus ofFIG. 1;

FIGS. 4 through 6 are sectional side views of the operating elements ofthe apparatus of FIG. 1 showing successive steps in the operation of themethods of the invention;

FIGS. 7 and 8 are, respectively, detail side and top sectional views ofanother gas permeable shell mold of the invention such as may be mountedin the apparatus of FIG. 1; and

FIG. 9 is an isometric view of a cast part from the mold of FIGS. 7 and8.

Referring to the drawings, and especially to FIG. 1 thereof, there isprovided a scalable melting and pouring chamber 12 with a sealableloading compartment 14 mounted thereabove having a door 15. A conduit 16having a slide valve 18 provides selective communication therebetween.

In chamber I2 is provided a melting crucible 20 having surroundinginduction coils 24 which form part of an induction melting furnace 22.Furnace 22 is mounted on vertically movable platform 26 by means ofinterposed load cells 30 to permit the measuring of the weight offurnace 22 and hence that of the molten metal in crucible 20. Platform26 is moved vertically by hydraulic cylinder and piston 32 mounted onsupport plate 34. Chamber 12 may be provided with a bottom closure 36mounted on support plate 34, and the latter may be mounted on dolly 38by scissors legs 41 for removal of furnace 22 from chamber 12.

More specifically as to the present invention, within chamber 12 andcompartment 14 is mounted a scalable mold container, generallydesignated 40, having a bottom opening 42 including an annular seal 44for sealing around the lower open end 46 of a gas permeable mold,generally designated 48, supported therewithin and extending downwardlytherebeyond (FIG. 2). Mold 48 is of the precision refractory, gaspermeable, shell type utilizing the lost-wax" technique and is wellknown and widely used in the art for casting a wide variety of ferrousand non-ferrous metals and alloys, such as steel. aluminum andnickel'chromium alloys, for example.

As shown in FIGS. 2 and 3, the novel mold of the invention includes,connected to its open end 42, a central vertical riser passage 50 with aplurality of mold cavities 52 clustered thereabout and connected toriser passage 50 by gate passages 54, the transverse cross section areadimension of the riser passage, as seen in FIGS. 3 and 8, for example.being at least about one square inch and preferably no greater thanabout 10 square inches in cross section area dimension and at leastabout five times as great as the transverse cross section area dimensionof a gate passage, as seen in FIGS. 2 and 7, for example. Mold 49, shownin FIGS. 7 and 8, is similar in its construction and dimensionalrelationships to mold 48. It includes a central riser passage SI and aplurality of longitudinally and circumferentially spaced gate passages55 connecting the riser passage to a plurality of mold cavitiescircumferentially clustered thereabout, both in longitudinally andtransversely radially overlapping relationship with regard to riserpassage SI. ln FIGS. 7 and 8, the mold spaces are shown as containingseparated discrete cast parts 90 with short gate stubs 92 (FIG. 9) inaccordance with the methods of the invention as hereinafter more fullyexplained.

Mold container 40, as best shown in FIGS. 4 through 6. includes a lowercup element 56 with bottom opening 42 and seal 44 (FIG. 2) and an uppercup element 58 with a gas communicating pipe 60. Each of said elementsis independently supported from above for movement into sealingrelationship with one another and for bodily vertical movement directlybetween an upper position within loading compartment 14 through conduit16 to a lower position in chamber 12 with the lower end 46 of mold 48beneath the central area of the surface 62 of molten metal in crucible20. To this end, upper cup element 58 is suspended by piston rod 64 ofcentral hydraulic cylinder 66 centrally mounted on the upper end ofcontainer 14 and lower cup element 56 is suspended by side piston rods68, 70, respectively, of hydraulic cylinders 72, 74 mounted on the upperend of container 14 at the sides of central hydraulic cylinder 66.Hydraulic cylinders 66, 72 and 74 are operated in the conventionalmanner to provide power for moving piston rods 64, 68 and 70 asrequired.

A pair of pans 76, 78 forming a movable drip guard are mounted withinloading compartment 14 above conduit I6 and are moved between their openand closed positions as shown in FIGS. 1, 4, 5 and 6 by suitable aircylinders (not shown).

Suitable vacuum pumps (not shown) are provided for evacuating loadingcontainer 40 through pipe 60, mold compartment 14 through pipe 80 andchamber 12 through pipe 82. A supply of inert gas, such as argon, isprovided in bottle 86 for controlling the vacuum pressure in container40 through pipe 60, chamber 12 through valve 88 and loading compartment14 through valve 89 as desired.

In operation, with door 15 of loading compartment 14 and slide valve 18open, and with lower container element 56 raised, crucible 20 may becharged by passing ingots directly through open drip guard doors 76, 78.Alternatively, cup element 56 may be removed and suitable tongs or thelike may be used for carrying ingots to crucible 20 by downward movementof piston rods 68, 70. Slide valve 18 is then closed and chamber 12evacuated through pipe 82 to a suitable high vacuum (about microns) atwhich time the ingots may be melted by supplying power to inductioncoils 24.

After melting is completed, according to another aspect of theinvention, the induction coils 24 surrounding crucible 20 holding themolten metal operate to stir it by moving it axially of coils 24upwardly in the center of the crucible to cause outward surface movementto carry dross and other impurities away from the central 5 area ofcrucible 20.

A molding cycle may be begun with the apparatus positioned as shown inFIG. 1. That is, with container cup elements 56, 58 separated, a mold 48is placed in bottom opening 42 of bottom cup element 56 with its 0 openend 46 therebelow (FIG. 2). Door of loading compartment 14 is thenclosed, and the upper element 58 of container 40 moved downwardly intosealing relationship with its lower element 56 (FIG. 5). Container 40and compartment 14 are then evacuated through pipes 60 and 80 to a highvacuum of about 10 microns. Then container 40, compartment I4 andchamber 12 are backfilled with argon to a suitable low vacuum (about 25inches Hg).

After all three are at the same vacuum pressure, according to themethods of the invention, as shown in FIG. 6, slide valve 18 is openedand sealed container 40 lowered by piston rods 64, 68 and 70 past opendrip guard doors 76, 78 until its open end 46 is below the surface 62 ofthe dross and impurity free molten metal in the central area of crucible20. Lower cup element 56 is kept above the surface 62. The molten metalis then caused to enter vertically positioned mold 48 by lowering thepressure in container 40.

According to another important aspect of the invention, after the metalhas solidified in mold cavities 52 and in at least part of their gatepassages 54, the still molten metal in riser passage 50, preferablywhile open end 46 is kept below the molten surface 62, is caused todrain back by gravity flow into the molten supply of metal in crucibleby raising the pressure in container 40 by admitting argon through pipe60. Thus, before open end 46 is moved above surface 62, the only metalleft in the mold (FIG. 7) except near its open end 46, are the desiredsolidified cast parts 90 with short gate stubs 92 (FIG. 9) which it willbe noted do not extend for the full length of the gate passages 55.

After molding is completed, container 40 is raised into compartment 14,drip doors 76, 78 are closed, and slide valve 18 is then closed.Thereafter, compartment 14 is raised to atmospheric pressure, its doorIS opened, container cup elements 56, 58 separated and mold 48 or 49removed to complete the molding cycle. The mold 48 or 49 is thenseparated from the contained parts by conventional methods, providing aplurality of discrete, unconnected parts (FIG. 9).

This aspect of the invention can perhaps best be understood inconnection with FIGS. 7 and 8 in which the cast parts (FIG. 9) are shownas present in the mold in the form of a plurality of discrete,unconnected parts 90 with short gate stubs 92, as is made possible bythe dimensional relationships of the central riser and gate passages asset forth above. The elimination of the solid metal riser which inheretofore conventional practice connected all the parts together makespossible uniquely high density packing of the mold cavities to theextent that it would be impossible as a practical matter to separate theparts were they connected to a solid metal central riser. Such is thecase with the mold of FIGS. 7 and 8, which illustrates the actualpractice of the invention in the casting of golf iron heads (FIG.

When it is desired to replenish the supply of metal in crucible 20, suchmay be done while maintaining the pressure in chamber 12 by placing aningot in an appropriate pair of tongs in place of lower containerelement 56, evacuating and pressurizing compartment 14 with argon,opening slide valve 18 and lowering the ingot into crucible 20 by pistonrods 68, 70.

What is claimed is:

I. In casting apparatus having a sealable melting and mold pouringchamber,

a scalable loading compartment mounted on said chamber and valve andconduit means communicating between said chamber and said compartmentthat improvement comprising:

a scalable mold container having a bottom opening for sealing around thelower open end of a gas permeable mold supported therewithin andextending downwardly therebeyond said mold container including upper andlower cup elements movable into sealed relationship with one another acrucible in said chamber having surrounding induction coils for holdingand stirring molten metal to cause outward surface movement thereofalong its surface to carry impurities away from the central area of saidcrucible power means including piston means independently supportingsaid cup elements from above for relative movement into said sealedrelationship and for movement between said compartment and said chamberthrough said valve and conduit means to said central area of saidcrucible and means for selectively varying the pressure of said chamber,compartment and container to fill said mold after lowering saidcontainer with the lower open of said mold beneath the surface of moltenmetal in said central area of said crucible and permit loading andunloading said mold from said container in raised position by relativemovement of said cup elements within said compartment while maintainingthe chamber pressure by closure of said valve and conduit means.

2. Casting apparatus as claimed in claim 1 further comprising a movabledrip guard mounted within said loading compartment between said valveand conduit means and said cup elements in raised and separatedposition.

3. ln casting apparatus having a sealable melting and mold pouringchamber,

a sealable loading compartment mounted on said chamber and valve andconduit means communicating between said chamber and said compartmentthat improvement comprising:

a sealable mold container having a bottom opening for sealing around thelower open end of a gas permeable mold supported therewithin andextending downwardly therebeyond said mold container including upper andlower cup elements movable into sealed relationship with one anotherpower means for supporting said elements for relative movement into saidsealed relationship and for moving said container between said chamberand said compartment through said valve and conduit means a meltingcrucible for holding molten metal mounted within said chamber beneathsaid container and means for selectively varying the pressure of saidchamber, compartment and container to fill said mold after lowering saidcontainer with the lower open end of said mold beneath the surface ofmolten metal in said crucible and to permit loading and unloading saidmold from said container in raised position within said compartmentwhile maintaining the chamber pressure by closure of said valve andconduit means.

4. Casting apparatus as claimed in claim 3 further comprising a movabledrip guard mounted within said loading compartment between said valveand conduit means and said container in raised position.

5. Casting apparatus as claimed in claim 3 wherein said power means arefluid piston means independently supporting said cup elements.

6. Casting apparatus comprising a melting crucible having surroundinginduction coils for holding molten metal a scalable mold containerhaving a bottom opening for sealing around the lower open end of a gaspermeable mold supported therewithin and extending downwardlytherebeyond, said mold container including upper and lower cup elementsmovable into sealed relationship with one another power means includingpiston means independently supporting said cup elements from above forrelative movement into said sealed relationship and for movement towardssaid crucible to lower the open end of said mold beneath the surface ofmolten metal in said crucible and means for relatively varying thepressure within said container to fill said mold after lowering saidcontainer with the lower open of said mold beneath the surface of moltenmetal in said central area of said crucible and permit loading andunloading said mold from said container in raised position by relativemovement of said cup elements.

a a t a

1. In casting apparatus having a sealable melting and mold pouringchamber, a sealable loading compartment mounted on said chamber andvalve and conduit means communicating between said chamber and saidcompartment that improvement comprising: a sealable mold containerhaving a bottom opening for sealing around the lower open end of a gaspermeable mold supported therewithin and extending downwardlytherebeyond said mold container including upper and lower cup elementsmovable into sealed relationship with one another a crucible in saidchamber having surrounding induction coils for holding and stirringmolten metal to cause outward surface movement thereof along its surfaceto carry impurities away from the central area of said crucible powermeans including piston means independently supporting said cup elementsfrom above for relative movement into said sealed relationship and formovement between said compartment and said chamber through said valveand conduit means to said central area of said crucible and means forselectively varying the pressure of said chamber, compartment andcontainer to fill said mold after lowering said container with the loweropen of said mold beneath the surface of molten metal in said centralarea of said crucible and permit loading and unloading said mold fromsaid container in raised position by relative movement of said cupelements within said compartment while maintaining the chamber pressureby closure of said valve and conduit means.
 2. Casting apparatus asclaimed in claim 1 further comprising a movable drip guard mountedwithin said loading compartment between said valve and conduit means andsaid cup elements in raised and separated position.
 3. In castingapparatus having a sealable melting and mold pouring chamber, a sealableloading compartment mounted on said chamber and valve and conduit meanscommunicating between said chamber and said compartment that improvementcomprising: a sealable mold container having a bottom opening forsealing around the lower open end of a gas permeable mold supportedtherewithin and extending downwardly therebeyond said mold containerincluding upper and lower cup elements movable into sealed relationshipwith one another power means for supporting said elements for relativemovement into said sealed relationship and for moving said containerbetween said chamber and said compartment through said valve and conduitmeans a melting crucible for holding molten metal mounted within saidchamber beneath said container and means for selectively varying thepressure of said chamber, compartment and container to fill said moldafter lowering said container with the lower open end of said moldbeneath the surface of molten metal in said crucible and to permitloading and unloading said mold from said container in raised positionwithin said compartment while maintaining the chamber pressure byclosure of said valve and conduit means.
 4. Casting apparatus as claimedin claim 3 further comprising a movable drip guard mounted within saidloading compartment between said valve and conduit means and saidcontainer in raised position.
 5. Casting apparatus as claimed in claim 3wherein said power means are fluid piston means independently supportingsaid cup elements.
 6. Casting apparatus comprising a melting cruciblehaving surrounding induction coils for holding molten metal a sealablemold container having a bottom opening for sealing around the lower openend of a gas permeable mold supported therewithin and extendingdownwardly therebeyond, said mold container including upper and lowercup elements movable into sealed relaTionship with one another powermeans including piston means independently supporting said cup elementsfrom above for relative movement into said sealed relationship and formovement towards said crucible to lower the open end of said moldbeneath the surface of molten metal in said crucible and means forrelatively varying the pressure within said container to fill said moldafter lowering said container with the lower open of said mold beneaththe surface of molten metal in said central area of said crucible andpermit loading and unloading said mold from said container in raisedposition by relative movement of said cup elements.